Master Spas spa filter (4CH-935)

Master Spas Eco-Pur (5" OD)

Replacement numbers

Unicel 4CH-935, Pleatco PWW35L

Fits Master Spas Eco-Pur (5" OD).

Diameter 4-15/16" (125 mm)Length 9-1/4" (235 mm)35 sq ft

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Unicel4CH-935
PleatcoPWW35L
Filburnot found in Filbur catalog
Topv-groove semi-circular handle
Bottom2" female SAE thread
Ø 4-15/16" (125 mm)9-1/4" (235 mm)Side view · end views belowTopBottom
Top: v-groove semi-circular handle
Bottom: 2" female SAE thread
Drawn to scale from the listed diameter and length. Handles, threads and closed ends are drawn as symbols, not to scale. 35 sq ft media.

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For Master Spas, 4CH-935 cartridge sits in Master Spas Eco-Pur (5" OD). The cross-reference prints Unicel 4CH-935; Pleatco PWW35L. 4-15/16" across, 9-1/4" long, top v-groove semi-circular handle, bottom 2" female SAE thread, 35 sq ft.

PWW35L carries this note from the catalogs: Unicel: replacement for 5" OD Eco-Pur systems; must verify OAL.

4CH-935 is easy to confuse on the Master Spas table. 4CH-252 differs by Unicel 4CH-252, Pleatco PMA20-F2M, 4-5/8" diameter, 8" long, top molded cone handle, bottom 2” male thread/MPT, 25 sq ft, OEM X268521, note says Unicel: Master Spas original has 4-3/4" OD. 4CH-949 differs by Unicel 4CH-949, Pleatco PWW50L, Filbur FC-0172, 13-1/2" long, 50 sq ft.

Filbur does not have a number on this row. Search PWW35L or the Master Spas part you pulled out of the spa.

Left blank on purpose: no Filbur equivalent found in Filbur catalog; no model/model-year fitment in sources; Unicel lists no OEM part number for this brand entry.

Where those figures are printed: Unicel 2026 Replacement Guide on 4CH-935 (OEM cross reference (Master Spas section), PDF p.45 (printed p.41); spec table PDF p.8 (printed p.4)). Pleatco 2023 Catalog on 4CH-935 (Unicel-to-Pleatco cross reference, PDF p.47).

If you know the Master Spas model and not the part number, use the Master Spas filter by model and year lookup.

Check the cartridge you removed

Measure diameter, length, and both ends, then compare them with the figures above. The steps are in the measuring guide. Why the bottom decides whether it seals: open-end vs threaded filters. Power, the retainer, and not running the spa empty: how to install a cartridge. Brand notes: Master Spas Eco-Pur filters. Number formats: how Filbur, Unicel and Pleatco numbers compare.

The same 4CH-935 number is also on the Nordic Hot Tubs, Waterway Plastics pages.

Other Master Spas cartridges

All 13 Master Spas spa filters

Every number on this row, on one screen: cross-reference lookup. Published clean and replace intervals for this cartridge, and a buy link for the numbers above: replacement schedule and reorder. The interval comparison by brand: calculator.

Cleaner and test strips

Hose rinse and soak steps are in how to clean a cartridge. Named cleaners and strips are in filter cleaners and test strips.

Filter cleaner and test strips

Sources

Not in sources: no Filbur equivalent found in Filbur catalog; no model/model-year fitment in sources; Unicel lists no OEM part number for this brand entry.